Project Summary Metal exposure has increased dramatically through the years with increased development of industry, agriculture, and manufacturing. Lead (Pb) has been a centerpiece for metal exposures with its numerous health effects impacting almost every organ system in the body. Monitoring of Pb and other metals is typically done using simple blood tests, but blood levels only reflect recent exposure levels. With the short half-life of blood, even serial measurements can have a significant amount of error relative to cumulative exposure and will reduce our ability to relate exposures with the lifetime health risks associated with occupational work. Bone is the body's primary reservoir for Pb and has been shown to reflect cumulative exposure over many years to decades, and, thus, is a much better biomarker for chronic health risks associated with occupational exposures. For decades researchers have studied bone Pb using x-ray fluorescence. However, the applicability of this tremendously valuable technology is significantly limited by several factors including lack of portability, long measurement times, and licensing needs that restrict where it can be used. In this proposal we address these issues by developing a novel portable KXRF bone Pb measurement system with the advantages of using a higher energy approach, while drastically improving the portability and applicability of the technology. In the proposed research, we will develop and validate our novel KXRF technology to measure Pb in bone in vivo and identify motor function associations with cumulative Pb exposure. In summary, the specific aims for the proposal are: 1) Build, optimize, and validate the portable KXRF system using in-lab samples; 2) Validate the portable KXRF system for in vivo measurement in a group of 100 people; and 3) Test the hypothesis that motor dysfunction is associated with higher cumulative Pb exposure. At completion of this study, a novel portable KXRF measurement system will be validated for use in populations previously inaccessible by current technology restrictions and can lead to future health studies of relevant at-risk populations. The proposal will advance the goals of the NIOSH Exposure Assessment Program by developing a new tool for worker surveillance of critical biomarkers to occupational health. The NIOSH Sector Agendas for Construction and Manufacturing have a priority area in identifying health hazards and musculoskeletal disorders. Pb exposure is a primary concern for construction workers as metal exposures are a common health risk for workers. Pb monitoring is a centerpiece to metal and electronics manufacturing and recycling, and cumulative exposure assessment is critical in identifying the lifetime risks to these workers. In the future the technology developed as part of this proposal can be advanced for use in a variety of metal exposure assessment settings and surveillance programs. In addition to the valuable technology, the proposed training and experience will prepare me for a career as an independent researcher for the development and application of more novel tools for exposure assessment in occupational health.